Peel and cube the potaotes. Boil in water until soft enough to easily cut with the side of a fork, 8-10 minutes. Drain and allow to cool.
Hard boil the eggs unless using store-bought (already hard boiled) eggs. Allow to cool.
Finely chop the red onion, red bell pepper, hard boiled eggs, and chives.
In a large bowl, combine the potatoes, red onion, bell pepper, hard boiled eggs, and chives. Add the vinegar, mayo, mustard, and sweet relish. Stir until everything is well combined. Add salt and pepper to taste.
Notes
You can use any vinegar if you don't have rice vinegar handy (white vinegar, or apple cider vinegar would be best). You can use dill pickle relish instead of sweet if you prefer, but I like the sweetness it adds. You can also use green onion instead of chives, or even swap for cilantro. If you are making the salad ahead (the night before), wait to stir in the chives or green onion until just before as the flavor will intensify some as the salad is stored.